| 【Objective】This paper is to study the effects of a Cr ( Ⅵ ) reducing strain Exiguobacterium sp. EH5
(hereinafter called strain E) on the phytotoxicity and phytoavailability of Pakchio seedlings under Cr ( Ⅵ ) stress. 【Method】
The effects of strain E on the growth and concentrations of chlorophyll, protein, malondialdehyde (MDA), superoxide
dismutase (SOD) and chromium in Pakchio seedlings under Cr ( Ⅵ ) stress were investigated by pot culture experiment, in
which the bacterial suspension with a volume ratio of 1% (bacterial suspension OD600 nm ≈ 4) was added into the hydroponicnutrient solution. 【Result】(1) Under the experimental conditions, when the concentration of Cr ( Ⅵ ) was higher, the Cr ( Ⅵ )
toxicity showed greater inhibition effects on the growth of Pakchio seedlings and their protein and chlorophyll synthesis. After
adding strain E, at the same maximum concentration of Cr ( Ⅵ ) (5 mg/L), compared with the group without adding strain E，
the stem length, root length, fresh weight, total chlorophyll and protein content of Pakchioi seedlings increased by 98.10%, 5.32%,
90.49%, 10.07% and 11.11%, respectively; (2) With concentration increasing of Cr ( Ⅵ ) stress, the MDA content in the leaves
of Pakchoi seedlings increased, the SOD activity was ascend in first and descend at last with concentration of Cr ( Ⅵ ) increasing
. After adding strain E, at the same concentration of 1-5 mg/L, the MDA content in leaves of Pakchoi seedlings decreased by
19.60%, 17.05%, 58.85%, 28.19% and 11.66%, respectively, compared with that in group E without adding strain E. When the
concentration of Cr ( Ⅵ ) stress was ≤ 4 mg/L, the activity of SOD enzyme in the inoculated group decreased compared with that
in the non-inoculated group under the same concentration. Then, with the increase of concentration of Cr ( Ⅵ ) ( ＞ 4 mg/L), SOD
activity in the group with strain E was 11.51% higher than that in the non-added group. (3) The Cr content in the roots, stems and
leaves of Pakchoi seedlings was higher with the increase of concentration of Cr ( Ⅵ ) stress. After adding strain E, Cr content in
the roots, stems and leaves of Pakchoi seedlings decreased compared with that in the group without strain E.【Conclusion】The
addition of strain E could alleviate the growth inhibition and oxidative stress from Cr ( Ⅵ ) on Pakchoi seedlings by reducing the
bioavailability of Cr ( Ⅵ ) by Pakchoi seedlings. |
